Background: Distal radius fracture is a common fracture encountered in fracture clinics. One of the common complications of this fracture is restriction of rotational movements of the wrist and forearm. Identification of factors affecting this loss of motion is of importance. This study was designed to identify the factors that may be responsible for loss of rotational motion of wrist and forearm in those extra articular distal radius fractures that are associated with ulnar styloid fracture.Methods: 47 patients with extra-articular distal radius fracture were enrolled in a prospective case control study from March 2005 to December 2006. pre and post operation. These were all stable extra-articular distal radius fracture that were treated by closed reduction under general anesthesia and long-arm casting. 24 patients had associated ulnar styloid fracture without extension into the joint and 23 others had no ulnar fracture. The patients had their final clinical follow-up after 6 months. The rotational movements of wrist and forearm were assessed for both groups by an independent observer. The pre and post operation findings were compared.Results: Ultimately the 23 patients with intact ulnar styloid had an average of 8.9 degrees less supination (compared with their non-broken side), and the ones with ulnar styloid fracture had 25.44 degrees average loss of supination (p < /em>